Percussion keyer for an electronic musical instrument

ABSTRACT

In an electronic musical instrument having a plurality of selectively operable keys associated with key switches and keyer circuits; a keyer circuit is turned ON to give out a tone signal by a trigger voltage derived from the key switch through a series-interposed capacitor and is subsequently turned OFF gradually by the charging operation of the capacitor. When the key switch is at a rest state, the capacitor is connected with a discharging route to prepare for the next operation of the key switch.

United:: States Patent Adachi et al. 51 Mar. 28, 1972 [541 PERCUSSION KEYER FOR AN 3,247,303 4/1966 Mi lho ..84/l.l3 ELECTRONIC MUSIC-AL'lNST-RUMENT" 3,333,433 5/1968 3. Sharp ..84/l.26 v i 3 3,465,088 9/1969 Kohis ..84/l.26 7 2'2 olwmlmbmh' 3,141,919 7/1964 Mabuchi. ...84/l.26 5 *9 Y 3,535,972- 10/1970 Teranishi ..84/ l.26 731 Assignee: Nippon Gakkl Selzo Kabushiki 1mm,

Hamamatsu-shi, Shizuoka-ken, Japan Primary Examiner-Lewis H. Myers Assistant Examiner-Stanley J. .Witkowski [22] Filed June 1970 Attorney-Flynn & Frishauf [2]] Appl. No'.: 49,053

- v [57] ABSTRACT v [30] Foreign Application Priority Date 7 r i .in an electronic musical instrument having a plnrality cf selec- June 25 1969 Japan 4 9 tiveiy operable keysassociated with'key switches and keyer 3 septa 1969 6 8 v t 'circuits;' a ke'yer circuit is turned ON to give out a tone signal by a trigger voltage derived from the key switch through a se- 521 05.0. ..s4/-1.26,s4/'1. 13 "P- andYis' subsequemly fumed OFF 511 rm. Cl.,.... ..Gl0h 1/02 gradually by the charging Operation of the capacim when [58] FieldofSearch ..s4/1.13,-126,1.09,1.1,DIG.7, the keyswiwhisatareststal,thecapaciwrisconnected with 34/D1G 3, DIG, 23 a discharging route to prepare for the next operation of the I key switch. 56 R i C'tcd e I 11 Claims, 12 Drawing Figures UNITED STATES PATENTS p I 3,180,919 4/1965 sq g e 4/1.6 f

P'A'TENTEB M28 1972 SHEET 2 OF 2 PERCUSSION KEYER FOR AN ELECTRONIC MUSICAL INSTRUMENT BACKGROUND OF THE INVENTION This invention relates to percussion keyers for use in electronic musical instruments and more particularly to percussion keyers capable of producing a complete envelope of a keyed tone signal for every depression in the consecutive key depressions.

The tone envelopes of percussive sounds produced by conventional percussion instruments such as a cymbal, triangle, castanets, iron Xylophone and the like generally have a characteristic which builds up rapidly immediately after key operation and gradually decays with time.

In percussion keyers which have been practically used in electronic musical instruments of the type referred to above, a single modulation circuit which is set from an inoperable to operable state interlockingly with the operation of any of the keys to produce a desired'en'velope' wave' signal is provided to be operated in common to all keys so as to modulate tone signals produced by the selective operation of any of the keys with the output signals from the modulation circuit.

With a percussion keyer utilizing such a modulation circuit, when respective keys are repeatedly operated with a time interval shorter than the necessary recovering time of the modulation circuit, the second and succeeding musical tones are included in the attenuation period of the first musical tone so that the second and succeeding musical tones will not be produced or if produced as incomplete musical tones. For this reason, when performance is conducted at an especially high tempo there will result musical tones greatly different from those produced by an ordinary percussion instrument.

SUMMARY OF THE INVENTION It is therefore an object of this invention to provide a novel percussion keyer for an electronic musical instrument which can produce complete envelopes of a keyed tone signal for every depression even in the rapidly repeated key depressions.

More particularly, according to this invention for use in an electronic musical instrument having a plurality of selectively operable keys, there is provided a percussion keyer for each key comprising an active circuit element such as a transistor constituting a keyer circuit which is turned ON by a keying switch interlocked with the key and subsequently turned OFF by the charging action of a capacitor which is connected to be charged through a DC impedance element, such as a resistor. A source for generating a tone signal having a predetermined pitch is associated with each active circuit element to provide an output signal.

According to a modified embodiment of this invention a touch responsive signal source is provided which produces a pulse signal having a voltage level proportional to the degree or speed of depression of the associated key and the generated pulse signal is applied to the active circuit element to vary the operating point thereof. The charging action of the capacitor determines the envelope of the tone signal produced by the musical instrument substantially resembling that of an ordinary percussion instrument. Further the so-called touch responsive effect can be provided so as to vary the maximum amplitude level of the musical tone according to the touching force applied on the key.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side view, partly in section, of the operating mechanism of a key of an electronic musical instrument having a plurality of keys which are operated selectively;

FIG. 2 shows a connection diagram of one example of the novel percussion keyer suitable for use in an electronic musical instrument having key operating mechanisms as shown in FIG. I;

FIG. 3 shows a typical output waveform appearing at the output terminal of the transistor shown in FIG. 2;

FIG. 4 shows a connection diagram of a modified percussion keyer embodying this invention;

FIG. 5 shows a typical output waveform appearing at the output terminal of the transistor shown in FIG. 4;

FIG. 6 shows a connection diagram of a still further modification of thisinvention;

FIG. 7 shows a typical output waveform appearing at the output terminal of the transistor shown in FIG. 6;

FIGS. 8 and 9 show connection diagrams of other embodiments of this invention;

FIG. 10 shows a typical output waveform appearing at the output terminal of the upper transistor shown in FIG. 9;

FIG. 11 is a side view of a modified key operating mechanism; and

FIG. 12 shows an equivalent circuit of the key operating mechanism shown in FIG. 11.

DESCRIPTION OF THE PREFERRED EMBODIMENTS As shown in FIG. 1 an operating mechanism of a key of an electronic musical instrument, for example an electronic piano or organ, utilizing the novelpergussionkeyer comprises a plurality of keys 13 (only one of them is shown) pivotaliy mounted at its rear end on a support 12 secured to a frame 11. Each key is normally held in the horizontal position by means of a tension spring 14. A rod shaped actuator 17 is secured to the lower surface of the key to control one or more keying switches contained in a keying switch box 16 secured tothe lower surface of the frame 11 in a manner later described when the key 13 is depressed as shown by an arrow 15. Near the outer end of the key is provided an integral depending leg (or skirt) 19 having a slot 18 for controlling the stroke of the key. The lower end of the leg 19 extends through an opening 20 of frame 11 and stoppers 21a and 21b made of soft material such as felt or cloth are secured to the upper and lower surfaces of the frame at portions contained in the slot 18 to alleviate mechanical shock at the time of depressing the key.

With reference now to FIG. 2 which shows one example of a percussion keyer embodying this invention, a tone signal source 32 generates a tone signal having a predetermined pitch specific to the associated key. The tone signal source 32 is connected to an input electrode of an active circuit element, for example, the base electrode of an NPN-type transistor TR via a resistor R The collector electrode of the transistor TR is connected to a grounded highest potential source terminal 33p through a resistor R and to an output terminal 34 through a coupling capacitor C,. The emitter electrode of the transistor TR is connected with the movable contact 350 of a keying switch 35 through a resistor R and a capacitor C The movable contact 35a is provided to cooperate with two stationary contacts 35b and 35c which are connected to negative source terminals 33m and 33m respectively at 9 volts and 12 volts, for example. One negative terminal 33m (hereinafter designated as l2v. terminal) having a larger potential difference with respect to the grounded terminal 33p is connected thereto through seriallyconnected resistors R and R and the juncture 36 between these resistors is connected to the base electrode of transistor TR for providing a base biasing voltage. A resistor R is connected between the juncture 37 between the resistor R and capacitor C and the other negative terminal 33m (hereinafter designated as 9v. terminal). It is to be understood that the movable contact 35a is held in engagement with one stationary contact 35b connected with -9v. terminal 33m when the associated key is not operated, but is switched to the other stationary contact 350 connected with the l2v. terminal 33m upon depression of the key. As a result the potential of the juncture 37 between the resistor R and capacitor C is substantially equal to 9v. while the associated key is not operated, but suddenly changes to 1 2v. when the key is operated.

According to this invention the values of the resistors R R and R are selected such that so long as the key is not operated a reverse bias voltage is applied across the base-emitter junction of the transistor TR to render it nonconductive whereas when the associated key is operated to momentarily apply the -l 2v. power voltage to the juncture 37 through the capacitor C, a forward bias voltage is applied across -the base-emitter junction so as to render the transistor conductive.

The percussion keyer constructed as above described operates as follows:

So long as-the associated key is not operated, the movable contact 35a of switch 35 is engaging with the contact 35b connected to 9v. terminal 33m, so that transistor TR, is set at an inoperable state thus producing no output signal. At this time, capacitor C is not charged. When the associated key is operated the movable contact 35a is switched to the stationary contact 35c connected to l2v. terminal 33m, with the result that the potential of the juncture 37 between the resistor R and capacitor C is rapidly changed from 9v. to l2v., thus turning ON transistor TR,. Then the capacitor C is gradually charged through resistor R so as to vary the potential at the juncture 37 from l2v. to 9v. In this manner, when the charging operation of the capacitor C is completed, the capacitor C is charged to 3v. and the potential of the juncture 37 again assumes -9v. thus turning OFF the transistor TR, again. Accordingly, the operating point of the transistor TR, which is turned ON at the moment when the associated key is operated will be lowered gradually by the charging operation of the capacitor C 1 Consequently, the tone signal having a predetermined pitch generated from the source 32 and applied to the base electrode of the transistor TR, is amplified by the transistor TR, to be taken out through the output terminal 34. As above described since the operating point of the transistor TR, is gradually lowered by the charging action of the capacitor C the envelope E, of the tone signal e, appearing at the output terminal 34 representing the maximum amplitude at the initial moment decreases gradually as shown in FIG. 3. As is well known in the art since the attenuation characteristicof the envelope E, is determined by the time constant Td, of the charging circuit comprising the capacitor C, and resistor R it is possible to cause the envelope of the tone signal e, appearing at the output terminal 34 to resemble that of a desired percussion instrument by the suitable selection ofthe time constant. When the associated key is released the movable contact 35a is switched back from the contact 350 to thecontact 35b and as a result the potential of the juncture 37 is rapidly changed from 9v. to 6v., but this does not affect theoutput since the transistor TR, is kept nonconducting. Then the capacitor C is gradually discharged through resistor R, so as to vary the potential of the juncture 37 from 6v. to -9v. In this manner, when the discharging operation of the capacitor C is completed, the potential of the juncture 37 again assumes 9v. to be ready for the next switch operation.

With the illustrated percussion keyer as the envelope of the maximum amplitude of each tone signal can be determined as desired to resemble a desired tone envelope of a percussion instrument, it becomes possible to vary respective tone envelopes as desired irrespective of the manner of operating the respective keys. In other words, it is possible to produce musical tones closely resembling ordinary percussive sounds.

FIG. 4 shows a modified percussion keyer which is identical to that shown in FIG. 2 except that an integrating circuit 40 comprised by a capacitor C and a resistor R is connected between the juncture 37 between the capacitor C and resistor R and 1 2v. terminal 33m Then, the build up portion of the envelope E of the maximum amplitude of the tone signal e,

can be controlled by the integrating time constant Ta which is equal to the product of the capacitance of the capacitor C and the resistance of the resistor R of the integrating circuit 40. As a result, as shown in FIG. 5, the waveform of the output signal appearing at the output terminal 34 builds up more slowly than that shown in FIG. 3.

In another modified percussion keyer shown in FIG. 6 a small resistor R, and a diode D poled not to pass the charging current but to pass the discharging current are connected in parallel with the capacitor C As a result the diode D does not affect the charging current for the capacitorC,

which flows during the ON period of the transistor TR,

so that charging is performed in the same manner through the resistor R, as in the circuits shown in FIGS. 2 and 4. But the discharging operation of the capacitor C is effected at a higher speed. Thus, it is possible to decrease the period during which the associated key is operated and is then released so that this modified embodiment permits more frequent operation of the key. In this embodiment, even through a keying switch 35 for controlling ON and OFF operations of the transistor TR, is a single pole signal throw type, the discharging operation of the capacitor C, is carried out quickly.

FIG. 8 shows another modification of this invention wherein a transistor TR,, corresponding to the transistor TR, shown in FIGS. 2, 4 and 6 to act as an amplifier is constructed as a selfoscillation circuit by providing a resonance circuit 50 comprising a capacitor C and an inductor L which are connected in parallel between the base and emitter electrodes thus constituting a damped oscillator itself and eliminating the tone signal source 32 shown in FIGS. 2, 4 and 6. The resonance frequency of the resonance circuit 50 is selected to be equal to that of the tone signal source 32 so that the percussion keyer shown in FIG. 8 operates in the same manner as those shown in FIGS. 2, 4 and 6 with more simple circuit construction. While in FIG. 8, the transistor TR, is shown as an emitter tuning type self-oscillation element, it will be clear that the oscillation circuit may take any one of a base tuning type, collector tuning type, Colpitts type or Hartley type self-oscillation circuit. In addition, the oscillation circuit may be comprised of a capacitor and a resistor instead of a capacitor and an inductor.

In a still further modification of the percussion keyer shown in FIG. 9 the circuit is constructed to variably control level of the maximum amplitude of the output signal appearing at an output terminal 342 by varying the depression force of the associated key, while the level of the maximum amplitude of the output signal appearing at the output terminal 34 or.34l or the operating point of transistors TR, or TR,, is constant regardless of the depression force of the key in the embodiments shown in FIGS. 2, 4, 6 and 8.

More particularly, according to this modified embodiment, there are provided a permanent magnet 61 secured on the rear side of the leg 19 and two magnetic sensitive semiconductor elements 63a and 63b supported on an arm 62 secured to frame 11, as shown inFlG. 1, in such a position to pass magnetic flux produced by the magnet '61 in a manner to be described later.

As shown in FIG. 9, these two magnetic sensitive semiconductor elements 63a and 63b are connected in series with a fixed resistor R and a variable resistor R, across the grounded terminal 33p and a 20 v. terminal 64. The juncture between the two elements 63a and 63b is coupled to the base electrode of an NPN-type transistor TR through a resistor R,,. With this connection the resistors R R,,,, the two elements 63a, 63b and the magnet 61 contained in a rectangle 60 cooperate with each other to act as a touch responsive signal source for varying the base bias voltage of the transistor TR, in accordance with the magnitude of the key depression force as will be discussed later in more detail. One element 63a is positioned with respect to the magnet 61 such that while the key 13 is not operated it will pass through a minimum quantity of the flux from the magnet 61 but will pass through an increased quantity of the flux in proportion to the degree of depression of the key. On the other hand the other element 63b is positioned such that it will pass through a maximum quantity of the fiux while the key is not operated but will pass through a decreased quantity of the flux in proportion to the degree of depression of the key. With this arrangement while the key is not operated one element 63a manifests a highest internal resistance whereas the other element 63b a minimum internal resistance, thus applying a minimum bias voltage to the base electrode of the transistor TR, to maintain it in its OFF state. When the key 13 is depressed, however, one element 63a gradually decreases its internal resistance while the other element 63b gradually increases its internal resistance in proportion lto the extent of depression of the key thus gradually inoperated.

creasing the bias voltage of e manner, the transistor TR is turhed i The emitter electrodeof the l2v. terminal 33m and to its base electrode through a re* sistor R The collector electrode of the transistor .TR, is connected to 9v. terminal 33m through a'r esistor R 5 and to the v emitter electrode of the transistor TR through a capacitor C,

and a resistor R The juncture 1371 between the capacitor C, i

and resistor R is connected to 9 v. terminal 33m, via a resistor R when the key is transistor TR, is connected to I The percussion-keyer shownin FIG-f9 operates as follows.

opposite terminals of the capacitorC are both connectedto the '9v. terminal 33m, respectively through the resistors R and R the capacitor C, will not be charged. 7

Upon depression of the key l3,'the changes in resistances of the elements 63a and 63b turn on the-transistor TR, whichin turn triggers, via the capacitor C the transistor TR, to become conductive'so as to produceat the output terrriinal 342 an output signal as shown in FIG. '10 which rapidly builds. up and then gradually attenuates owing to the charging action of the capacitor C5 through the"resis'torR As a result, it is possible to obtaina tone signal frofrn the source 32 whose en,- velope varies in a 'substantially similar manner to that of a desired percussion instrument.'-The level'of the maximum arnplitude E, of the output signal appearing at the output terminal 342 is variedas shown by doubleheadedarrows in FIG. 10 in proportion tO:tI'l depth 0. '7 I nitude 'of the key depressing fore "Thi sl becau'se that where the depth of thedepresse'd key is 's the base bias voltage of the transistor TR is low so thatsmallcurren'ts flow throu'gh j the transistors TR,'a nd butas-the depthof the depressed key increases the base biasvoltage of transistor TRiin-v creases, thus increasing the currents flowing through the transistors TR and TR;. It will be clearthat the attenuation period Td of the envelope E3, of the rriaX-irrium amplitude of the output voltage at the output terminal which radially builds 5 up and gradually attenuates varies dependent upon the poten- 1 ha] difference across the capacitor C which is charged through the resistor R Thepotential difference across the capacitor C is determined mainly bythe collector voltage of the transistor TR when it is turned ON. The collector voltage of the transistor TR when it is turned QN is determined by the I voltage drop across resistor R caused'by the current varying l in proportion of the depth of depression of the' key I3, as above described. Consequently, as shown in FIG. 10, the attenuation period Tdof envelop of the depressed key 13. y, v

The build up characteristic of the output signal appearing at the output terminal 342 varies dependent upon the depression 5 speed of the key and it will be noted that as the depressing I e.E -increases with the depth force increases, the output signal builds up more rapidly. i

Further it will be' cl'ear that only one magnetic sensitive ele- Q ment can be used instead of twoi' Alternatively, as'shown in FIG. l=l,' the magnetic sensitive 5 element may be replaced by a coil 63l which is positioned coil 631 while the key is in its] inoperative position but the 4 quantity of the flux interlinking through the coil increases with 3 the depth of depression of the key. FIG. 12 shows a circuit dial gram of a portion of'the percussion keyer shown in FIG. 11.

plitude proportional to variations in the magnetic flux or the depression speed of the key,v by utilizing this voltage as the base bias voltage of the transist'or TR similar operation as that of the circuit shown in FIG. 9 can be provided. However,

it is to be noted that where sucha coil utilige i theggut totgt responsiye signalsourcecomprises} perr'r anentmagnet sig na l v arie s inproportion to the depression speed of the key and not to the depth of the depression as in the previous embodiment. For this reason it is also possible to mount the coil .631 such that it interlinks a maximum quantity of the flux from the magnet ,61 when the key is not depressed and the l most suitable applications. Corresponding portions of FIGS. 2,

4, 6, 8, 9 and 12 are designated bythe same reference letters to simplify the description. I i i Typical values of various resistors utilized in these figures are as follows:

Resistors Values in ohm a, 82 to R. urn R, 3.: kn R, 22 kfl R, 39.0 to R. 22 kn R, 100 n R. 2.2 kn n, 470 n R" s n R" 22 kn R, 2.2 kn a 22 kn R,, 10 kn kg. :9 kn. i u 9 5 1a,, 22 k0 1 R" 47 tn i R,, [0 an 3 Capacitors Values in microfarad c, 4.1 ,tr. c, 4.7 gr. C; I. I f. c, 0,: ,tr. I c, 0.41 r. Inductor Value in henry Whatwe claimis: I I l. ln'an electronic musical instrumenthaving a plurality of playing keys, a percussion keyer for and associated with each of the respective keys comprising: i an active circuit element having an input electrode, an output electrodearid a trigger electrode; a first DC voltage .s'ourcehaving a first voltage of a magnitude which is sufficient to render said active circuit element inoperative; a resistor coupling said first DC, voltage source to said trigger electrode; V l v a second DC voltage so irce having a second voltage of a magnitude which is sufficient torender said active circuit element operative when coupled to said trigger electrode; a capacitor and keying switch means connected in series circuit with each other, said series circuit being connected between said trigger electrode and said second DC voltage source, said keying switch'means being selectively actuated by its respective key to selectively couple said second DC source to said trigger electrode; and a discharge means connected between said first DC voltage source and said capacitor for discharging said capacitor when said'k'eyin'g switch means is not actuated. 2. A percussion keyer according to claim 1, wherein said acv tive circuit element is a transistor constituting an amplifier, such that substantially no flux of magnet 61 interlinks through 565 and there is further provided a tone signal source connected to said input electrode of said transistor.

3. A percussion keyer according to claim 1 comprising a resonance circuit associated with said active element which 7 l l comprises with said active element a damped oscillator. Since the coil 63] generates "a voltage pulse having an am- 4. A percussion keyer according to claim 1, wherein said keying switch means includes a touch responsive device associated with each of said keys-and charging-said capacitor witha voltage responsive to the fotce of key depression.

5. The percussion keyer according to claim 4 wherein said and a circuit element operative in response to the flux produced by said magnet. v

6. The percussion keyer according to claim wherein said circuit element comprises a further active circuit element which varies its internal resistance according to the quantity of 5 the magnetic flux produced by said magnet, which flux passes through said element.

7. The percussion keyer according to claim 5 wherein said circuit element comprises an inductance coil which induces a a diode connected between said first DC voltage and the other end of said'capacitor which is connected to said trigger electrode, said diode being in a direction such that it becomes backward biased for a charging current of said capacitor and forward biased for a discharging current of said capacitor.

9. A percussion keyer according to claim 1, wherein said keying switch means includes a further active element which is rendered conductive when said keyer is actuated.

10. A percussion keyer according to claim 1, wherein said keying switch means couples said capacitor to said first DC voltage source when it is not operated, and couples said capacitor to said second DC voltage source when it is operated by its respective key.

11. vA percussion keyer according to claim 10, wherein said keying switch means is a single pole-double throw switching element. 

1. In an electronic musical instrument having a plurality of playing keys, a percussion keyer for and associated with each of the respective keys comprising: an active circuit element having an input electrode, an output electrode and a trigger electrode; a first DC voltage source having a first voltage of a magnitude which is sufficient to render said active circuit element inoperative; a resistor coupling said first DC voltage source to said trigger electrode; a second DC voltage source having a second voltage of a magnitude which is sufficient to render said active circuit element operative when coupled to said trigger electrode; a capacitor and keying switch means connected in series circuit with each other, said series circuit being connected between said trigger electrode and said second DC voltage source, said keying switch means being selectively actuated by its respective key to selectively couple said second DC source to said trigger electrode; and a discharge means connected between said first DC voltage source and said capacitor for discharging said capacitor when said keying switch means is not actuated.
 2. A percussion keyer according tO claim 1, wherein said active circuit element is a transistor constituting an amplifier, and there is further provided a tone signal source connected to said input electrode of said transistor.
 3. A percussion keyer according to claim 1 comprising a resonance circuit associated with said active element which comprises with said active element a damped oscillator.
 4. A percussion keyer according to claim 1, wherein said keying switch means includes a touch responsive device associated with each of said keys and charging said capacitor with a voltage responsive to the force of key depression.
 5. The percussion keyer according to claim 4 wherein said touch responsive signal source comprises a permanent magnet and a circuit element operative in response to the flux produced by said magnet.
 6. The percussion keyer according to claim 5 wherein said circuit element comprises a further active circuit element which varies its internal resistance according to the quantity of the magnetic flux produced by said magnet, which flux passes through said element.
 7. The percussion keyer according to claim 5 wherein said circuit element comprises an inductance coil which induces a pulse voltage of a variable amplitude proportional to the rate of change of the flux produced by said magnet, which flux passes through said element.
 8. A percussion keyer according to claim 1, wherein said discharge means includes: a further resistor connected between said first DC voltage source and the terminal of said capacitor corresponding to the end thereof which is connected to said keying switch means; and a diode connected between said first DC voltage and the other end of said capacitor which is connected to said trigger electrode, said diode being in a direction such that it becomes backward biased for a charging current of said capacitor and forward biased for a discharging current of said capacitor.
 9. A percussion keyer according to claim 1, wherein said keying switch means includes a further active element which is rendered conductive when said keyer is actuated.
 10. A percussion keyer according to claim 1, wherein said keying switch means couples said capacitor to said first DC voltage source when it is not operated, and couples said capacitor to said second DC voltage source when it is operated by its respective key.
 11. A percussion keyer according to claim 10, wherein said keying switch means is a single pole-double throw switching element. 